Which of the following is not a commonly accepted method or device to prevent backsiphonage?

The correct answer is the option that represents something that does not prevent backsiphonage. Cross-connections are, in fact, a potential problem rather than a solution; they can allow contaminated water to flow back into the drinking water supply, which is the opposite of preventing backsiphonage.

In contrast, vacuum breakers, air gap separation, and back pressure units are all recognized methods of preventing backsiphonage. Vacuum breakers work by breaking the vacuum that can form in plumbing systems, allowing air to enter and preventing backflow. Air gap separation involves physically separating the supply of potable water from any potential source of contamination by a vertical distance, which effectively prevents backsiphonage by ensuring there is no physical connection between the two. Back pressure units are designed to maintain pressure in the system and help prevent any unwanted backflow.

Thus, understanding the roles and functionalities of these devices helps clarify why cross-connections should not be considered a method for preventing backsiphonage.